The effects of catecholamines on electrolyte movements in, and electrical properties of, frog skin have been extensively studied for several decades. To our knowledge these hormones have always been applied to the corium side of the skin, never to the epidermal side. Thus, one of the most singular actions of this hormone when applied to the epidermal side has been missed; namely stimulation of active inward Na ion transport at doses which, when applied to the corium side, would also stimulate the skin glands and, thus, conceal the epidermal effect. The externally elicited epidermal effect is not possible in the absence of C1 ions, even in the short-circuited skin, as we have recently discovered. It is planned to further study this externally elicited catecholamine effect. In particular, we are interested in investigating: The nature of the receptor site; the dose-response relationship; a possible interaction with pitressin; the significance of anion permeability; the effect on osmotic water flow.